Beta-eucryptite Ceramic Composite for Low Thermal Expansion
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Solution Overview
Problem
Current materials with low thermal expansion coefficients struggle to maintain dimensional stability across a broad temperature range, particularly from cryogenic conditions to above room temperature, and often have inadequate mechanical properties and complexity in manufacturing complex shapes.
Innovation Solution
A process for producing ceramic composites with a thermal expansion coefficient of less than 1x10^-6 K^-1 within the range of -150 °C to 150 °C using a β-eucryptite matrix and nanometric silicon carbide (n-SiC) nanoparticles, allowing for improved mechanical and thermal properties, and enabling pressureless sintering in a conventional furnace to achieve high relative density and versatility in shape and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If glass ceramics are used to achieve low thermal expansion coefficient, then thermal expansion control is improved, but mechanical properties (fracture resistance) deteriorate
Solution Approach 1:
The patent creates a composite ceramic material combining β-eucryptite (providing negative thermal expansion) with cordierite and mullite phases (providing structural strength and positive thermal expansion). This composite approach allows the material to achieve near-zero thermal expansion coefficient while maintaining high fracture resistance through the reinforcing effect of the cordierite-mullite network structure.
2Stability of the object's composition
If materials with negative thermal expansion coefficient are used, then thermal expansion control is improved, but fracture resistance deteriorates due to anisotropy
Solution Approach 1:
The patent distributes the negative thermal expansion property locally to specific β-eucryptite crystallites within the composite, while the surrounding cordierite-mullite matrix provides local structural support and crack resistance. This local quality differentiation allows each phase to perform its specialized function without compromising the other.
Solution Approach 2:
By combining β-eucryptite with cordierite and mullite in a composite structure, the patent mitigates the inherent weakness of negative expansion materials. The cordierite-mullite matrix compensates for the low fracture resistance of pure β-eucryptite, creating a composite with both desired thermal expansion properties and adequate mechanical strength.
3Ease of manufacture
If traditional glass processing methods are used, then manufacturing simplicity is improved, but mechanical properties and density deteriorate
Solution Approach 1:
The patent employs advanced sintering parameters including controlled heating rates, specific holding temperatures (1000-1200°C), and extended holding times to achieve complete densification and phase development. These parameter optimizations transform the manufacturing process from simple glass processing to a controlled ceramic sintering process that produces dense, high-strength materials with tailored microstructures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting ceramic materials exhibit high dimensional stability, improved mechanical properties, and the ability to produce complex shapes with densities greater than 90% of theoretical density, enhancing their applicability in precision technologies and aerospace sectors.
Implementation Method 1
Some mineral phases of this family have a negative TEC, which makes it possible to use them in composites with a controlled, customised TEC. The family of lithium aluminosilicate (LAS) ceramics and glass ceramics is frequently used for this purpose... the phase with the negative expansion is β-eucryptite (LiAlSiO4), due to the large negative expansion in the direction of one of its crystallographic axes.
Implementation Method 2
The traditional method for manufacturing materials with an LAS composition is the processing of glass to produce glass ceramics... The preparation is performed by means of a simple process for manufacturing nanocomposite powder, which is shaped and sintered in the solid state using different techniques
Data Source
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AI summary
The invention relates to a method for obtaining ceramic compounds and to the resulting material, comprising the following steps: using as a starting compound an LAS component having composition LixAlySizOw, wherein x varies between 0.8 and 1.2, y varies between 0.8 and 1.2, z varies between 0.8 and 2 and w varies between 4 and 6; mixing the LAS component with SiC nanoparticles, thereby obtaining a stable homogeneous suspension; drying the resulting suspension; shaping the material obtained; and, finally, sintering the material obtained in the previous step. The resulting material has a density greater than 98% of theoretical density and can be used in the aerospace industry, microelectronics and precision optics.